Process for producing fibrous alkali metal titanates



United States Patent 3,328,117 PRGCESS FOR PRODUCING FIBROUS ALKALI METAL TITANATES Robert S. Emslie, Chadds Ford, Pa., and Hugh C. Gulledge, Newark, and George L. Lewis and 0swin Burr Willcox, Wilmington, Del., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del, a corporation of Delaware No Drawing. Filed May 10, 1963, Ser. No. 279,580 23 Claims. (Cl. 23-51) This invention relates to improved fibrous alkali metal titanates and to novel methods for their preparation.

More particularly, it relates to selectively synthesizing improved, Water-insoluble fibrous alkali titanates in various diameters and lengths and by means of a novel non-fluid reaction process in which observance of certain temperature controls and other conditions insures the selective production of such fibrous products in predominant desired colloidal, pigmentary or insulating size ranges.

US. Patent 2,833,620 discloses the preparation of fibrous dialkali metal titanates corresponding to the formula M O(TiO in which n is 6-7 and M is an alkali metal having an atomic number greater than 11, i.e. sodium, potassium, rubidium, and cesium by reacting in the presence of Water a water-soluble basic oxygen-containing alkali metal compound, such as an alkali metal hydroxide, with an oxygen-containing titanium compound, such as titanium dioxide, at a temperature of at least 400 C. under a pressure of at least 200 atmospheres. US. 2,841,470 discloses the preparation of fiber of the general formula M O(TiO where n=2-3 by dissolving a non-fibrous alkali metal titanate in a fused, heated salt melt of an alkali metal chloride or fluoride, maintaining a portion of the molten halide saturated With the dissolved compound as the fibrous alkali metal titanate is formed, and separating the crystallized titanate fibers from the salt by Water extraction.

In accordance with this invention, selective production can be effected of an improved fibrous alkali metal titanate in either predominantly colloidal, pigmentary or insulating type, by recourse to novel process techniques which are readily adaptable for continuous commercial operation and from which recovery is obtained of relatively large, increased yields of fiber product per unit charged to the system. Advantageously, this is achieved without recourse to costly pressure equipment and procedures, or experiencing the difllcult containment, heating and handling problems incidental to liquid molten salt mixture use.

These and other major advantages are attained in this invention which embodies the discovery that observance of a precise control over the temperatures of calcination Within a range of from about 200 C. to 1150 C., and preferably from about 600-1100" C. in a continuous operation to react a non-fluid (substantially free from any liquid or gaseous phase) reaction mixture comprising a basic oxygen-containing alkali compound, such as an alkali metal hydroxide or carbonate, and an oxygen-containing titanium compound, such as titanium dioxide, in such proportions as will yield a fibrous titanate product containing a ratio of TiO /M O (wherein M is an alkali metal) ranging from 4:1 to 9:1 and preferably from 4:1 to 7: 1, provides an effective control over the development and ultimate length and diameter of such product. In consequence, production will be assured of a titanate material of greatly improved uniformity, e.g. its fibers will be in the desired dimensions and free of substantial percentages of undersized and oversized material. Thus, when in accordance with the invention, relatively low,

from about 200-850 C. and preferably from 600-825 32,328,117 Patented June 27, 1967 ice C. temperatures are resorted to, the fibrous material will be found to comprise particles predominantly (that is in excess of 50% and preferably at least thereof) which are in colloidal dimension to range from .0050.1 micron in diameter with lengths at least 10 times said diameter; when calcination temperatures in the range from about 850-975 C. are undertaken, a fibrous product predominantly in pigmentary size range will result, having a particle diameter ranging from 0.1-0.6 micron with lengths ranging from 10 to times the said diameter; and when temperatures ranging from about 975 C., to 1150 C., and preferably from about 975 C. to 1150 C. are utilized, one obtains a fibrous product of predominantly greater dimension having a particle diameter ranging from 0.6-3.0 microns with length of from 100-1000 times the diameter and longer which possesses great utility as an insulating or reinforcing material. These size ranges of products can be readily determined by examination with an electron microscope at a magnification at 25,000 to 50,000 times actual size and measuring directly the enlarged image of the product.

In producing the improved fibrous alkali metal titanates of this invention, a dry, compacted intimate reaction mixture or charge is first prepared by suitably dry blending the various reactant components and then briquetting or otherwise conventionally converting the blend into lump or compacted form. The compacted charge can comprise a mixture of a basic oxygen-containing alkali metal compound, particularly a hydroxide or carbonate of sodium or potassium, with a titanium compound, particularly titanium dioxide, with the latter preferably being in a suitably divided form for uniform dispersion throughout the mixture. The equivalent molar ratio of titanium compound to alkali metal compound, calculated as titanium dioxide to alkali metal oxide (TiO /M O wherein M preferably consists of K or Na) is variable, and can range from 2:1 to 8:1. Preferably, such ratio ranges from 3:1 to 5:1. Alternatively, an alkali metal halide salt, particularly a chloride of potassium or sodium, can be introduced as a component of the charge, and in amounts ranging from about 5-65% by weight based on the total weight of the charge. In such event, the amount of basic oxygen-containing alkali compound present can range from about 7-65 and the amount of titanium oxygencontaining compound used can range from about 20- 80% by weight to provide a 0.25 to 20 mole ratio of TiO /M O.

The resulting compact is then converted to the desired colloidal, pigmentary or insulating form of fibrous titanate, by calcining it in conventional furnacing means such as a direct-fired batch or rotary kiln or shaft type furnace and on a continuous basis. The calcination can be conducted over periods of time ranging from about 0.25 to 16 or more hours, depending upon the nature and composition of the dry reaction charge, the type of fibrous titanate being produced, and the particular temperatures and furnacing means utilized. For example, in the calcination, the reaction charge can be continuously fed to the cooler temperature end of a direct-fired rotary kiln or shaft furnace which is suitably maintained within the required temperature range, and from which the converted reaction product is continuously withdrawn from the hotter end of the furnace.

The fibrous titanate-containing calciner discharge recovered is then purified and separated from undesired reaction or other products through water or acid leaching treatment. Fibers are further separated by exfoliation. Thereafter it can be dried or otherwise treated to recover the desired final form of fibrous material. This process of purification and exfoliation can be carried out simultaneously with other processes like papermaking where crude kiln discharge is added directly to the beater. De-

pending on the form or type of fibrous product obtained, the material will be found to be highly useful in all applications where its inertness and other physical characteristics (like refractive index, aspect ratio, surface nature, and others, etc.) are requisite. For example, when such product is in prepondernantly colloidal form it provides to be highly useful as an adjuvant for incorporation into lubricants, such as silicone grease to improve lubricant properties at higher temperatures. Similarly, when the product is preponderantly in pigment size range, it will be found to be advantageously useful in pigmenting paper or in compositions used in coatings on paper and folding boxboard. In such applications it will be found to be of enhanced value due to its highly desirable properties of opacity, retention, brightness and the like which are attributable to its fiber length, diameter and melting point.

We have found, for example, that in making a sheet of paper of approximately 50 pound ream weight (500 25" x 40" sheets, to the ream), with an ash content of 6%, only 75% as much pigmentary potassium titanate, by weight, is required to achieve the equivalent opacity or dry hiding power of the sheet as is produced by 100% of a standard grade of water dispersible, anatase titanium dioxide pigment. This unexpected result is the more remarkable inasmuch as the refractive index of potassium titanate is only about 2.3 while that of anatase titanium dioxide is 2.5 and would be expected to impart a higher opacity, rather than a lower one, to the pigmented paper composition.

Likewise production of a preponderantly fibrous inan 11' ID. by 13" internal length ceramic-lined kiln, rotating at 2 r.p.m. and fired directly with a gas burner by injecting the flame into one end of the kiln. On completion of the calcination, the reaction product discharge from the kiln was leached until freed of unreacted material and the compressed briquetted fibers were then crushed to a 4 mesh size and dispersed for 5 to 10 minutes in 4 gallons of distilled water, employing a conventional high speed, high shear type blender in the process. The fibers were then exfoliated by first adjusting the dispersion to a pH of 10.5 with dilute acetic acid and then passing the slurry through a colloid mill about 45 times. This dispersion was then run through a basket type centrifuge provided with a nylon fiter cloth backed with cotton, dried, and evaluated. In colloid fiber processing the filtrate was saved while the filter cake was reslurried with 2 gallons of water and passed through the colloid mill an additional 4 times. Filtration through the centrifuge was repeated on the second dispersion. Filtrates were combined and acidified to a pH of 6.5 by adding a commercial cationic ion exchange resin while stirring for a period of 30-40 minutes. The resin was separated from the mix by filtration through a 200 mesh seive. To the filtrate was added a commercial anion exchange resin while stiiring for 30- minutes. This resin was removed through seiving prior to flocculation of the particles by the addition of 15 gms of alum in a 4% aqueous solution. Flocculated material was collected in the basket centrifuge. Filter cakes were dried at 95 C. and weighed. A summary of the results and products obtained are shown in the following Table I.

TAB LE I Composition of Reactor Mix,

Ingredients Parts by Wt.

T10 T101 M20 Reaction a Conversion to Fiber of Size, Percent Diameter (Rang Microns Time at Temp, (Hrs) Length (Range), Microns Size Category 1 Titania 1 C Colloidal; P Pigmentary; I=Insulating.

Example I The following series of colloidal, pigmentary and insulating forms of fibrous potassium or sodium hexatitanate preparation was undertaken by calcining various blends and ratios of the alkali metal and titanium compounds enumerated in Table I below. The TiO and other reactant ingredients employed were first dry-blended in a drum roller and then briquetted to approximately /2" x 1" x 1" size through a conventional compacting device at a presseure of 3300 lbs/sq. in.

The briquetted products were then calcined at the temperatures and for the time periods specified in Table I in 3 Example 11 Demonstrative of the effect of time and temperature on colloidal potassium titanate fibers in accordance with the invention, are the following series of calcinations applied to briquettes prepared from a master blend of TiO K CO and KC]. This blend was prepared by dry blending the ingredients in a drum roller in a weight ratio of 2 parts TiO /1 part K CO /1 part KCl (50% TiO 25% K CO and 25 KCl) where the TiO /K O mole ratio is 3.5/1. Briquettes of approximately /2 x l" x 1" dimention were prepared from this dry blend by compaction at a pressure of 3300 lbs. per sq. in.

Three pounds of these briquettes were calcined in an 11' ID. x 13" internal ceramic-lined kiln rotating at 2 rpm. and fired directly with a gas burner by injecting its flame into one end. Time at a temperature for vairous runs are shown in Table II below.

After calcination the calciner discharge was leached and purified as well as exfoliated as in Example I to provide the desired fibrous potassium titanate.

The time and temperature, the percent conversion to TABLE II fibrous material of the size range listed, and the analysis caicmation Calcination Percent Yield of of the water extracted product, as well as the size caten, C- Time, s- Colloidal-Size gory in which the product obtained fell are shown in said 5 Table III. 3.? g The calcined briquettes containing the fibrous material 775 11 from each run were charged to 1000 gal. tan-ks and 38g purged at 90 C. with demineralized water, timed at 300 3 gals. per hour for six days in the case where pigmentary and insulation grade fibers were formed (runs F through 815 5 48 A-l). Colloidal fibrous material (runs A through E) were gig Z8 treated in a manner similar to that described in Example 815 71 II. The leached fibers in bundles the shape of the 2;? ad g? briquettes originally fed to the kiln, were dried on trays 825 57 in an oven at 110 C. 825 50 In the instance of pigmentary sized fibers, exfoliation was performed by first dry grinding the dry material Samples of this colloidal size fibrous potassium titanate g g g ig i gg g nluxmg dlammeral' product were incorporated into silicone grease with dethe s g a i er 1 t a rg sired improvement and enhancement resulting in lubricat- 2O g; diluted i f gg z fi g g g mg Properties at relanvely high temperatures mineralized water and passing this mixture through a Example I cleaner consisting essentially of a wet cyclone separator to remove large particles of grit. Finally, the degritted A mixture containing 1 part of potassium carbonate, 2 Slurry p e e back through the atfrltlen 111111- parts of anatase titanium dioxide pigment and 1 part of The resultlrlg dlsperslen was then P p Into a 3000 potassium chloride was dry blended in a drum rollen gal. vessel and allowed to settle for two hours. The top The mole ratio of TiO:K O was 3.5 in the presence of 10% of the hqurd eemalnlng dlspersed fiber was e- 25 wt. percent potassium chloride. This material was then canted and transferred to another tarlk and Processed in pressed into cylindrical briquettes of approximately 4" 300 P r as follows: e dlspersed e Slurry x 1 size, which Were then continuously fed, at rates was neutrarrzedfe a P of PP Sf Wlth 25% Varying from 2045 per hour, into a gas fired mtary hydrochloric acid and fiocculated by adding 7 lbs. of poceramicqimd kiln with an internal diameter and 30 tassium chloride. Flocculated fibers were filtered on paper it. in length, heated by direct gas firing at the opposite to r eekes and were washed free of end. The bed temperature Within the kiln was adjusted to Chlorlde Wlth 3 4 Portlons of Water gals- The temperatures ranging from 600 at the feed port to 1200 filter cakes w Placed on trays and erled at 75 for C. at the exit, with a continuous increase in temperature 24 Molsture the e after lf average existing over the 30 ft. length. Residence time of the re- Dry filter Cakes were eXfOllatfid agflln by dry grind ng actants in the kiln was regulated at A2 to 6 hours being Pass e r mesh Screen: then rnlero'pulverrzed 115mg maintained by adjusting the pitch and rotary speed of the 40 Metels Dlsmtegraters, machine The fibrous P kiln. A uniform bed depth was maintained within the slum rltan'ete Pr were then p e SlZed and kiln, with the holdup amounting to anywhere between alyzed e p trle results as Shown 111 Table 150 lbs. to 450 lbs. of feed material for each run listed The 11151111171011 sleed fibers Shown were r ground in the series shown in Table III below. A total of 2000 m the manner descrflged for the ma m y slzed s, lbs. of briquettes containing the fibrous material were but were simply exfoliated by dry grinding and were then collected at the hot end of the kiln over each run period. formed into mats or felts of loose fibers and processed.

TABLE III Analysis of Water Extracted Product Conversion Tempera- Time (Hrs) to Fibers Size ture, C. at Temp. of size Mole Ratio Diameter Length Category 1 TiO /M O average, average, IIllCl'OllS 1111GT 0118 800 0.5 15 4.1 0.007 0.6 0 800 1.0 00 5.2 0.01 1.5 C 800 2.5 75 4.8 0. 02 2.0 0 300 3.5 83 6.7 0.03 3.0 O 375 3 75 4.5 0.2 2 P 875 6 95 5.2 .4 10 P 900 1 6.3 .2 2 P 900 3 90 5.8 .4 3 P 900 0 93 5.9 .5 12 P 925 1 4.2 .5 10 P 925 3 95 5.4 .5 15 P 925 6 98 6.8 .0 20 P 950 1 7.3 .0 15 P 975 1 9.2 1 50 I 975 3 6.7 1 75 I 975 5 99 5.8 1 100 I 1,025 1 35 4.9 1.2 75 I 1,025 3 97 5.7 1.3 100 I 1,025 0 99 6.0 2 150 I 1,050 0.75 95 5.6 2 I 1,050 1 95 7.2 1.5 100 I 1, 050 3 98 9.3 2.0 150 I 1, 050 0 99 6.3 3.0 I 1,075 1 95 4.3 2.0 140 I 1,075 3 98 9.1 3.0 I 1,075 6 99 6.4 3.0 150 I 1 C Colloidal; P =Pigmer1tary; I=Insulating.

Example IV In this example fibrous potassium titanate materials were prepared in the same manner and in the apparatus described in Example III but using as sources of titanium Example V Sodium titanate fibers in colloidal, pigmentary and insulation size ranges were manufactured employing the procedures and apparatus described in Example III, using dioxide, raw hydrous titania, the product from a comnierthe reactants, ratios and temperature conditions listed in cial sulfate process for producing anatase TiO pigment, (a) of Table V below and with the results therein shown. highly refined anatase pigment, ground rutile ore and In addition, mixed sodium and potassium titanate fibers beneficiated ilmenite. These reactants were mixed and were prepared in the same manner, utilizing the listed compacted with various sources and amounts of potasreactants, proportions and temperatures set forth in. (b) sium oxide, in the form of potassium carbonate, potasof Table V to obtain the results therein given. The pigsium bicarbonate in varying portions of potassium fluoride mentary potassium mixed titanate fibers were exfoliated and chloride salts as shown in Table IV below. The reby means of colloid mill treatment and were passed action temperatures listed are the average temperatures through this mill in a 1% slurry until the grit content at the time given. The analysis of the Water extracted (large sized particles) averaged less than 2% by Weight. product, size category and other results obtained are also The insulation sized materials were dispersed in distilled listed in the table. water and washed until chloride free. Examples of these TABLE IV Composition of Analysis of Water Ingredients Reaction Mix, Conver- Extracted Product Parts by Wt. Reaction Time sion to Size 'Iemp., (hrs) at Fibers of Cate- 0. Temp. Size, Mole Diamgory 1 Percent Ratio etcr Length T102 M Salt T102 M20 Salt (range) (range) 5 26 20 930 2.5 9 6. .5 0-20 13.... Hydmus Tltama K200 Km 44 21 930 2.5 93 5.3 .4 10-20 P 20 40 930 2.5 93 7.2 .4 10-20 P 24 11 65 930 2.5 95 403 .4 10-20 P 0---. 62 33 5 900 1.5 95 6.0 .6 10-20 P II. 30 1 900 1.5 95 5.4 .2 20-12 1:

. 54 26 2 900 1.5 96 7.1 10-1 J Anatase p1gment KHCO; 40% KF 60%KC1 44 21 35 900 L5 98 '4 H5 I, 40 20 40 900 1.5 98 5.0 .3 10-15 P 24 11 900 1.5 93 6.6 .3 10-15 F 62 33 5 950 2. 9s g9 .5 10-20 r; 60 30 10 950 2. 98 .9 .6 10-20 Rutle Ore KHCO KF 54 26 20 950 2.0 93 6.2 .7 10-20 P 44 21 35 950 2.0 98 6.7 .8 1020 P 800 1 50 4.1 .01-0.1 1-2 0 875 6 99 4.2 .07-. 15 1-5 P 925 0.5 90 4.9 0. 3-.5 5-15 P U.. 925 1.0 95 7.2 0. 2-.5 5-20 P v Benefic.Ilmenite.. K2003 KCl 2 1 1 925 2.5 98 6.3 0.1-.5 10-20 P W 925 5.0 99 7.9 0. 3-.5 15-30 P X 925 7.5 99 8.8 0. 2-.6 20-40 P Y 1, 025 1.0 95 5.6 1-2 50-100 I 1,025 2.5 99 6.2 1-3 75150 I 1 C=Colloidal; P=Pign1entary; I=Insulating.

runs are shown in runs A through K of (b) in Table V below.

TABLE V (a) Preparation of Sodium Titanate Fibers Ingredients Composition of Reaction Conver- Analysis Mix, Parts by Wt. sion to of water Temp., Time, Fibers Extracted Size 0. Hrs. of Size, Product, Category 1 TiO M20 Salt TiOz M20 Salt Percent Mole Ratio TiOz/MzO 850 1 100 4.3 0 850 3 100 4.9 0 925 0.5 50 5.3 P 925 1.5 7.9 P 925 3.5 95 4.9 P 975 0.5 60 5.8 P 975 2.0 5.7 P Anatase pigment NazCOa NaCl 3 1 5 1 1,025 1.0 50 7.3 I 1,025 2.0 6.4 I 1,025 3.0 7.9 I 1,025 6.0 99 8.9 I 1,100 1.0 30 5.9 I 1,100 2.5 90 5.8 I 1,150 5.0 99 6.6 I 2 1 6 1,050 2.5 96 6.3 I Anatase pigment NaOH NaCl 3 1 4 950 2.5 95 5.2 P 4 1 4 950 2.5 95 6.7 P NaHCO NaCl 2 1 4 1, 050 4. 0 9s 5. 7 I NaHCOs NaCl 3 1 2 900 2. 0 98 5.8 P Rutile ore NaHCO NaCl 1.5 1 2.5 975 2.5 98 6.3 P Na CO NaCl 1. 5 1 2. 5 975 3. 0 93 7.1 P Nazcog NaGl 1. 5 1 2. 5 975 4. 0 9s 6. 2 P

(1)) Preparation of Mixed Na-K Titanate Fibers Composition of Ingredients Reaction Mix, Conver- Analysis of Product Parts by Wt. sion to Size Temo, Time, Fibers Cate- C. Hrs. of Size, gory 1 Percent Mole Ratio TlOz/ Diam. Length T10 M20 Salt TiOz M20 Salt M avg, avg,

Microns Mierons A NaHCO KCl 1.5 1 2.5 800 2 60 6/1.5 NazO-0.5 K20 0.008 2.6 C B Rutile pigment. NaHCOg KCl 1.5 1 2.5 925 2.5 88 6/1.1 NazO-0.8 K20 0.3 35 P sas t 1 i252 2 tr ses-- a 1 Na 1.5 1 5. 1.0Na2 -1 2 0. E. iAnatase KOH NaF 2.5 1 2.5 1, 015 s 96 4.3/1Na2O-1K2O." 0.90 130 r I-.- Rutile ore N220 K01 70 23 7 850 3 92 C l C=Colloidal; P=Pigmeutary; I=Insulating.

Example VI Fibrous potassium titanate pigment was prepared by dissolving eleven parts of solid KOH pellets (83% KOH) or an amount of KOH equivalent to 9.2 parts (0.160 moles) in 5 mls. of water in a vessel to form a clear solution. 20 parts (0.25 mole) of TiO (TiO /K O=3/ 1) and 9 parts of KCl (24% KCl in dry mix) were added to the solution with 8111116161112 stir-ring to form a smooth paste which was placed in an oven at 150 C. and heated to dryness. The dry lump product recovered was then ground to pass a 30 mesh screen and the pulverized product was placed in a crucible and calcined at 945 C. for 70 minutes. Upon cooling, the mass was broken up into small lumps and soaked for two days in deionized water. Afterward, the lumps were leached free of KCl and excess KOH in a counter current flow of hot water and steam until the mole ratio of TiO /K O was determined to be 6 by analyses.

The recovered fibrous material was then separated into individual fibers by passing a 10% fiber-deionized water suspension through a colloid mill three times. The 10% fiber mix was diluted to gm./liter by adding further amounts of deionized water and was stirred. Heavier nonexfoliated material was allowed to settle out for 15 minutes and was separated from the lighter dispersed fibers by decantation. Sediment from this process was diluted to a 10% mixture again and passed through the colloid mill until complete dispersion was obtained when rediluted to 15 gm./liter.

The resulting dispersed fiber slurry was adjusted to a pH of 7.3 by adding sufiicient dilute HCl and the fibers water fiocculated by adding 5 mls. of 0.1 M MgSO water solution and filtered off. The pad of fibers collecting on the filter was then washed with three separate 1 liter portions of deionized Water to remove the fiocculating agents. The 26 parts of recovered fibers was dried in an oven at 100 C., cooled and passed through a 12 mesh screen to produce a 57% yield of free flowing pigment useful in papermaking. When so employed, it was found to'be easily dispersed in the beater.

Microscopic examination of the pigmenting fibers revealed that they averaged 5 to 50 microns in length and had a 0.1 to 0.6 micron diameter, with most being 0.3 micron in diameter.

Example VII Sodium titanate pigment fibers are prepared in substantially the same manner as described in Example VI. Twenty parts of Ti0 (0.25 mole) contained in 60 parts of wet raw anatase T10 from a sulfate hydrolysis process "for precipitating the TiO were mixed with 6.4 parts of NaOH pellets (0.16 mole) and 30 parts of NaCl and the resulting mixture was calcined at 940 C. for 75 minutes. Following flocculation and processing as in Example VI, the length of the fibers was found to be shorter than the potassium titanate fibers obtained in that example. That is, they were about 15 to microns long, and had diameters of the order of 0.2 to 0.6 micron. When processed in papermaking, this product was found to be practically no dififerent in performance over a pure TiO pigment prepared from the conventional hydrolysis of a titania sulfate solution pure T10 and that from the rutile ore.

Example VIII A mixture containing 600 parts of potassium carbonate, 1,200 parts of titanium dioxide, 600 parts of potassium chloride, the mole ratio of TiO /K O being 2.9/1 in the presence of 25 weight percent KCl, was dry mixed for 4.5 days in a drum roller. This material was then pressed into cylindrical briquettes approximately x 1" in size which were continuously fed at a 30 to 40 lb./hour rate into a rotary calciner of the type described in the foregoing examples. The bed temperature of the kiln has a profile of 750:25 C. at the feed entrance and 910125 C. at pigment exit, with a continuous gradient of temperature over the apparatus length. Residence time in the kiln was regulated to 2.5 to 3.5 hours by adjusting the pitch and rotary speed of the kiln and to provide about 1 to 2 hours calcination of the reaction mass at temperatures of from 875 C. to 975 C. Uniform bed depth was maintained within the kiln with a holdup amounting to 200 to 300 lbs. of feed material. A total of 1830 parts of briquettes containing the fibrous pigment were collected at the hot end of the kiln over a period of 69 hours. (The deficiency was due to about 250-300 lbs. of KCl which boiled out the feed port, loss of about 17 pounds of CO from the reaction and kiln holdup.) The briquettes were then placed in a 1000 gal tank and leached with C. demineralized water flowing at 3 gals./ hr. for 6 days. The water was continuously changed until the leachings were free of chlorine and the leachable caustic was removed from the fibers. The recovered fibrous titanate, in the shape of briquettes, were placed on trays, and dried in an oven at C.

Exfoliation of the dry fibers was performed by first dry grinding them to pass through a 4 mesh screen and then mixing them with demineralized water to form a 10% fiber slurry, This slurry was then passed through a conventional attrition mill set at 3 mils followed by dilution of the slurry to a 1.5% fiber content with additional demineralized water. This mixture was then passed through a cleaner apparatus consisting essentially of a wet cyclone separator to remove large particles of grit. Finally, the degritted slurry was reprocessed back through the attrition mill and the dispersion was allowed to settle for 2 hours. The top 10% of this liquid (300 gals.) containing the dispersed fiber was decanted and transferred to another vessel and processed in 300 gal. portions as follows: The dispersed fiber slurry was neutralized to a pH of 7.25 with 25% hydrochloric acid, then fiocculated by adding 7 lbs. of KCl. Flocculated fibers were filtered on paper to form cakes 26" x 26" x 1" and were washed free of chloride with 3 portions of water, 9 gallons each. The filter cakes were placed on trays and dried at 75 C. for 24 hours. Moisture in the cake after drying averaged 3 to 5%. Dry filter cakes were exfoliated again by dry grinding to pass a 4 mesh screen, then micropulverized. A total of 1,150 pounds of fibers (80% yield) were collected. The bulk density of the finished pigment was 5 lbs./ cu. ft.

and the fiber lengths varied between -40 microns with the average diameters of the product being 0.3 micron. 1000 pounds of this product was conventionally processed into a high quality magazine paper print of 70# ream weight wherein it proved to impart and provide better papermaking properties over a corresponding paper pigmented with TiO This was especially true in respect to offset lithography performance. In addition, the treated paper embossed much easier, with much less pressure being required.

Compared to the TiO treated paper, the fibrous titanatetreated paper product was outstanding in brightness and less abrasive. In off-set printing, less slitter dusting was noted, the ink drying more rapidly, while the print definition was highly satisfactory. Its decreased abrasion property is especially advantageous in that the life of the Fourdrinier wire becomes extended, and cutter blade wear and dusting on the sheet during cutting is decreased, as is printing press plate wear.

Example IX A paste containing 1000 parts TiO 500 parts K CO 200 parts K 50 700 parts KCl and 1,875 parts H O, was dried at 120 C. in a tray dryer and then briquetted into 1" x squares. The mole ratio of TiO /K O in the dry mix was 2.7/1 in the presence of 30% KCl. The briquettes, with a bulk density of 70 lbs/cu. ft., were fed into a 10 in. diameter by ft. ceramic lined shaft furnace to a depth of 8-11 ft. The rate of feeding was so regulated that residence time in the kiln was about 8 hours. The furnace was direct fired with a natural gas-air mixture such that the hot combustion gases passed up through the bed to provide a countercurrent flow of hot combustion products over the briquette bed Calcined fibrous product was removed from the bottom of the furnace by periodically opening its outlet grates. After about 6 hours of feed to a bed which started at a depth of four feet, the temperature profile is about 975 C. at the bottom and 750 C. at the top. At the end of such 6 hours of feed, the rate of movement through the furnace was controlled at one foot/ hr. so that the residence time at 875 C. to 950 C. was about 1.5 to 3.5 hours and held within that average rate for 60 hours. These temperatures were maintained by adjusting the gas flame used to directly fire the furnace and by adjusting the throughput rate. About 2050 parts of calcined mate 'al was produced.

Briquettes con ining the fibrous pigment product were processed in a 1000 gal. tank, exfoliated and dried as outlined in Example VIII. A total of 1100 lbs. of exfoliated fibers (91% yield) was obtained. The bulk density of the finished pigment averaged 5.1 lbs/cu, ft., its fiber lengths varied from 15S0 microns, and its diameters ranged from 0.09 to 0.31 micron, 600 lbs. of the product was incorporated into 40# ream weight magazine print to provide a paper having superior brightness, slitter dusting, print definition and embossing characteristics.

Example X A mixture containing 424 parts of sodium carbonate, 1100 parts TiO 200 parts of sodium chloride, the mole ratio of TiO /Na O being 6/2 in the presence of 1700 parts of NaCl (52% of the mix) were blended for 3 days in a drum roller. The resulting mixture was then briquetted and calcined in a rotary kiln as described in Example VIII The feed rate and flame temperature were regulated to hold the residence time of 1 to 2 hours at 900 Ci25 C. About 1200 lbs. of fibrous sodium hexatitanate material was obtained after leaching and exfoliating in accordance with the procedure outlined in Example VIII. The fibers averaged 0.67 micron in diameter with lengths up to 50 microns. These sodium hexatitanate fibers were found to be slightly softer and more flexible than the above potassium fibers. When incorporated into paper, these pigmentary fibers possessed brightness slightly superior to that obtained from fibrous potassium titanate pigment use.

Example XI A mixture of parts NaOH, 280 parts K CO 1250 parts TiO in ground rutile ore, parts NaCl, and 175 parts KCl were dry blended in a drum roller for a period of 3.5 days. The mole ratio of TiO /M O was 3.9/1, in the presence of 17% alkali chlorides. This material was Example XII A pulp beater was charged with 445 parts of 4% sulfite pulp-water slurry containing 18 parts of sulfite pulp then with 7,000 mls. of distilled water and stirred for 4 minutes. To this was added 1.88 parts of fibrous potassium hexatitanate pigment having an average diameter of 0.3 micron and lengths ranging between 40 and 150 microns, and an additional 4 minutes of stirring was undertaken. 1.78 parts of 20% starch solution and 17.8 mls. of 4% alum was then added with 4 minutes of stirring being applied for each ingredient.

The resulting slurry was placed into a proportionator and diluted to 12,600 mls. with distilled water, and thirteen 8" x 8" sheets of paper were then sheeted on a 100 mesh screen in a conventional type sheeting machine by withdrawing 970 mls. for each sheet. The dry weight for each sheet averaged 1.45 parts, equivalent to 25 lb. ream weight. Opacity, brightness and retention characteristics of these sheets were measured. The average of these sheets for various loadings is recorded in the following table:

TABLE VI Loading, Weight Percent Paper Properties Percent Percent Percent Opacity Percent Potassium Retained TiOa Titanate T102 Plus Titanate Waxed Nonwaxed Example XIII Employing the procedures of Example XII for a 13 sheet evaluation procedure, the following results were obtained when mixtures of pigmentary fibrous potassium titanates of this invention were employed in conjunction with a commercial grade TiO pigment. The potassium titanate fibers used for this series were slightly longer than those employed in Example XII, i.e., their lengths were 50 to 300 microns and their diameter was about 0.25 micron:

TABLE VII Loading, Weight Percent Paper Properties Percent Percent Percent Opacity Percent Potassium Retained TlOz Titanate TiO2 Plus Titanate Waxed Nonwaxed Example XIV A series of 25 lb. and 50 lb. ream weight sheets filled with a fibrous potassium hexatitanate pigment 16 to 40 microns in length and having an average 0.25 micron diameter, were prepared for comparison with similarly 5 prepared and Weighted sheets filled with anatase TiO pigment. The following are the comparative results:

Example XVI TABLE VIII.25 POUND REAM WT. SHEETS Percent Percent Percent Bursting Pigment Pigment Opacity Waxed Pigment Strength Addition Nonwaxed Retention Sulfite Pulp 53. 7 12 0 T102 10 58. 7 24. 2 9. 2 TiO 20 59.8 26.7 7.7 Potassium Titanate. 6 59. 7 21.2 20.0 Do 10 63. 4 28. 8 23. 1 D0 20 69. 6 38. 7 21.0

50 P0 UND REAM WT. SHEETS Sulfite Pulp O 72. 15.3 0 26, 2 T102 5 74.0 25. 5 6.8 26. 3 75. 2 30. 5 6. 8 25. 4 76. 8 36. 9 8. 3 25. 3 5 77. 0 32. 4 20. 0 25. 5 1O 80. 3 43. 9 23.1 24. 7 20 85. 5 53.1 24. 5 20. 4

Example XV Following the procedure outlined in Example XII, a series of lbs. ream wt. hand sheets were prepared, using fibrous sodium hexatitanate in the unleached crude kiln discharge as the pigmenting ingredient. This material averaged 25 microns in length and had an average diameter of 0.21 micron. The test results obtained in this series resulting paper to provide the results shown in Table X below.

In preparing the sheets, sulfite pulp was beaten in a conventional papermaker beater to a degree of 32 at a stock consistency of 4%. Fibrous potassium titanate pigment having a 10 to 45 micron length and average diameter of 0.275 micron or an anatase TiO pigment in the amounts specified in said table, were then added with the pulp which was then diluted and pumped to the headbox of the Fourdrinier machine. The pigmented-pulp slurry was then flocculated with alum in the headbox, with 2% alum on the OD. pulp weight being used throughout. In

no case was starch or rosin size used.

TABLE X Pigment Anatase-Ti0 Potassium Titanate Fibers Pulp Only Pigment Added, percent 1 5 10 15 20 5 10 15 20 0 Pigment Analyzed, percent 7.07 10. 49 13. 59 4. 44 8. 92 12.54 15.59 0 Pigment in Dry Sheet (percent). 2. 9 3. 3 5. 8 6. 3 3.0 6. 8 8. 8 12. 4 0 Pigment Retention (percent) 46. 5 55.0 46.7 68.4 75.9 69. 5 79.7 0 Dry Opacity (percent) 84. 0 84.1 87.4 88.9 85.4 90.8 93.2 94.7 75.1 Wax Opacity (percent) 57.5 58.4 65.6 67.0 51. 7 62.8 67. 9 72.1 22.6 Brightness G.E. (percent) 83.4 86.3 87.0 87.3 84.3 87.9 88.5 89. 3 79.6 Mullen Bursting Strength (lbs./

sq. in.) 24.0 26. 6 23. 4 21. 3 22. 7 15.8 10. 2 8. 5 27.4 Tear Strength: I

rig 47 52 47 42 39 42 44 48 50 Across 68 63 64 49 53 53 51 68 1 Added on dry pulp basis. Analysis on dry pulp slurry.

are shown in the following table.

The fibrous, water-insoluble alkali metal products of this invention in their colloidal, pigmentary or insulating form, vary in crystal structure depending on their history. The structure is that of the tetratitanate, hexatitanate or mixtures of both. They differ only in respect to sizethat is fibrous products with diameters ranging from 0.0050.1 micron and lengths at least 10 times the diameter are of colloidal size; those having diameters ranging from 0.1-0.6 micron and lengths ranging from 10 to 100 times their diameter are of pigmentary size; while products possessing diameters ranging from 0.6-3.0 microns and lengths ranging from 100 to 1000 times their diameter are of insulating or reinforcing type.

Essentially the invention entails an improved method for the selective preparation through selective control over the reactants and reaction conditions in a kiln process, of good yields on a continuous industrial basis, of predominantly (above 50% and preferably at least 80% or 90%) amounts of a fibrous colloidal, pigmentary or insulating titanate product. Although generally applicable to the preparation of alkali metal titanates, the process is especially useful for producing the preferred fibrous sodium and potassium titanates. Again, while described as applied to certain specific embodiments involving particular kiln calcinations, reactants, ratios, temperatures, times, etc., variance therefrom is contemplated. In general, any basic, water-soluble, oxygen-containing compound of an alkali metal oxide or salt which exists as the alkali metal oxide under reaction conditions (potassium, sodium, cesium, rubidium) eg an oxide, hydroxide, carbonate, bicarbonate, oxalate, nitrate, etc. or mixtures of such compounds can be used. Specific examples of such compounds include: Na O, NaOH, NaNO Na CO NaHCO Na C O K20, K2CO3, KNO3, KHCO3, K C O CSNO3, C5 0, CSOH, CS2CO3, CSHCO3, Cs C O Rb O, RbNO RbOH, Rb CO RbHCO Rb C O RbHSO and the like.

While Ti0 (titania) in either anatase or rutile anhydrous pigmentary or hydrated (orthotitanic acid) form comprises a preferred source of titanium for use in the invention, other titanium-oxygen compounds adapted to yield Ti under the reaction conditons can be employed. Examples thereof include the various sodium or potassium salts of titanic acid, e.g. meta or ortho titanates (M TiO or M TiO titanium hydroxide, titanyl sulfate (TiOSO or titanyl chloride. Similarly useful are certain types of titaniferous ores, such as rutile, ilmenite or beneficiated ilmentite, etc.

The source of titanium dioxide is probably the most dependent ingredient variable in the process. The size of the fiber and its rate of growth will depend upon the crystalline form of the TiO its particle size, history and impurity content. Within any given source of titanium dioxide, an ore for example, the particle size of the ore will also affect the fiber growth characteristics. The degree to which the ore is ground prior to its compounding with the salt if present and the alkali metal oxide source will bear importantly on the preparationof a suitable fiber of particular size range. This is also true in preparing the fiber from hydrated titania or titanium dioxide pigment sources. Generally, finely ground (passing 325 mesh) titanium dioxide sources yield a higher degree of small particle size fiber and require higher t mperatures to form materials of long fibrous nature. Coarse sources of titanium dioxide such as rutile (passing 60 mesh) yield fibers of intermediate range in predominantly pigmentary size. In explanation of this phenomena, it has been postulated that the formation of pigmentary fibers is a two step mechanism. In the first step, titanium dioxide is solvated in the salt matrix and reacts with the alkali metal oxide source to form an insoluble or rather less soluble fiber. These small fibers then at higher temperatures are redissolved and are recrystallized on the surface of larger fibers. It appears, therefore, that in very finely ground titanium dioxide or hydrated titania sources a predominance of colloidal material is formed rapidly, and that formation of larger fibers from this colloidal material is a slower process than large fiber formation directly from a relatively coarse TiO source.

On X-ray and chemical analysis, the products of this invention, depending on the temperature of calcination and the ratios of ingredients employed in their preparation, will be predominantly fibrous hexaor tetratitanate in accordance with the formulae M O-6TiO or M O-4TiO wherein M is selected from the above enumerated alkali metals, and preferably, is sodium or potassium. An optimum type fibrous pigment or insulation composition is obtained by calcining pellets of wellblended TiO /K CO in the molar ratio of 3/1 to 4/1 together with KCl (2550% by weight total ingredients) at substantially 875-1050" C. temperatures. Thereafter the granular product is leached or water extracted and is then milled to effect separation of the fibers which are then collected and dried. As will be noted in such preparation recourse is had to an alkali metal halide, the presence of which provides a salt matrix or solvent in which the reaction can take place to grow fibers of the desired pigmentary or insulating size. The metal halide employed preferably consists of a chloride or fluoride of the same alkali metal as that of the oxide or its equivalent employed for reaction with the titanium-oxygen compound. Usually, alkali metal chloride concentrations of from 10% to 65% by weight of the total mix are effectively useful. In potassium titanate preparation the presence of from l030% potassium chloride is most satisfactorily useful while with sodium titanate preparation from about 30-75% of sodium chloride is needed, The ratio of TiO /M O can vary within the range mentioned above but preferably ranges from 6/ 1 to 6/3, with the best conversion to fiber being brought about when the indicated 3/1 to 4/1 TiO /K O ratio of components is approximately maintained. If use is made of a dissimilar salt mixture, for example in the preparation of a sodium titanate with a fused potassium halide salt, the fibrous product will contain both sodium and potassium. Both alkali metal fluorides and chlorides with alkali metal chlorides being preferred for employment since they prove particularly suitable in the formation of fibers with a tetratitanate structure as well as the hexatitanate structure. The temperature required for the conversion in the presence of fluoride salts will be found to be somewhat lower than that necessary when chloride salts are present.

Generally, the higher the temperature the higher will be the solubility in the salt matrix of both the reactants and the fibers produced. About 5% to about 65% salt by weight is generally satisfactory for a continuous process wherein the fibers are being formed over a short time period. The quantity of salt needed in the reaction mix depends on two or three variables. The first variable is the degree to which the reactants are ground, the second variable is the temperature at which the operation is to be carried out, while the third variable is the type fiber being formed, either potassium or sodium titanate fiber. In forming sodium titanate, higher concentration (40- 65% of the total mix) of salt is necessary for good fiber conversion, whereas in the case of potassium fiber formation anywhere from 540% proves suitable, depending upon temperature and the material desired as the endproduct. Increasing the salt concentration in a particular reaction mix provides a more uniform product and the distribution of a particular particle size becomes less scattered. By this is meant that the scattering of oversized and undersized material is decreased to a point such that the product is more uniform in length and diameter than it is when lower concentrations of salt are used. At low concentrations of salt it has been found that fibers of the smaller dimension are predominant. This refining action appears to take place by redissolving the quickly formed smaller titanate fibers and their recrystallization on the surface of larger less soluble fibers. This refining action is particularly noticeable for fiber diameter, rather than fiber length. Nonacicular material is redissolved in the fused salt and then deposited on the surface of a larger fiber and renders the material, particularly in the intermediate size ranges, free of very small fibers and nonacicular particles. Although the salt functions primarily as a flux in which the reaction takes place, it also to some unknown degree participates in the fiber formation and by a mechanism not clearly understood. When potassium titanate fibers are formed from titanium dioxide and potassium carbonate in, for example, a sodium salt, titanate fibers are obtained containing sodium in the lattice structure. Conversely, when sodium titanates are formed in the presence of potassium chloride one obtains potassium in the fiber structure. It will be understood that the presence or addition of relatively small amounts of various salts or impurities, including those of Mg, Al, Zn, and Ca, will affect the temperature of calcination required, the ingredient ratios used, the growth characteristics, and will generally alter the process of fiber formation. To compensate for these variances, use is contemplated of calcination temperatures substantially in excess of the range limits which have been indicated, particularly in those instances where production of pigmentary and insulating forms of titanate products is being undertaken.

Any known method for intimately mixing or blending the reactant ingredients prior to calcining them in dry, non-fluid form or compacted form can be resorted to. Higher density compacts afford better control of product fiber length and diameter and hence are preferred for use. These can be obtained in several ways. Thus a paste of the ingredients can be added to the kiln directly or evaporated on trays to form a solid mass which can then be broken into desirable sizes, or a dry mix of the powdered mixture can be pelletized or briquetted to suitable size through use of standard pelletizing and briquetting equipment and techniques to form the lumps or pellets to be fed to the kiln.

While the temperature of calcination is the dominant control variable in the process for forming a particular fibrous product, it may range generally from 800-1100". However, as previously indicated, the fiber lengths are controlled primarily by the particular temperature at which the reaction mix is calcined. That is, use of the lower portion of such range, preferably from 600-850 (3., provides fibers of predominantly colloidal size, while the temperature range from 875-975 provides predominantly intermediate or pigmentary size fibers; while temperatures ranging from 975l050 C. results in the production of relatively long fibers, or predominantly insulation size material. These ranges apply to potassium titanate formation. When sodium titanate fiber formation is undertaken, temperatures ranging up to about 25 higher for each category are resorted to.

The temperature of calcination used for the production of a particular fiber is also dependent upon the source of titanium dioxide used in the reaction charge. Generally, the finer the titanium dioxide particles, the higher will be the temperature required; for example, a higher temperature is required for raw hydrous titania than for pigmentary TiO which in turn requires a higher temperature than crude TiO such as a titaniferous ore. The tempera ture of the salt matrix, when present, must be high enough to redissolve the small particle size fibers in order to recrystallize them on the surface of larger fibers already in formation. In finely divided mixes, formation of small fihers is relatively rapid and higher temperatures are therefore required for dedissolution. If a coarsely-ground titanium dioxide source is present, fiber formation is usually directed from the TiO source through the salt matrix and directly onto the fiber. Therefore, redissolution is not necessary. For this reason fiber formation usually takes place at a lower temperature.

The type of heating employed appears to have little effect upon the growth of a given fiber. Therefore, the type of furnacing or calcination means used is not important in comparing a shaft furnace with a rotary kiln, for example. Rather, it is the length of time to which the reactants are subjected to the prescribed temperature which is important.

The time and temperature needed for production of the desired fiber size is related to the Ti0 /M O mole ratio, the salt content (when present) and the size and density of the compacted feed charge. The fibers will be found to grow quite rapidly at first, usually Within a half hour from commencement of the calcination. In extending the period of treatment at a given temperature, the fibers grow at the expense of smaller, previously formed fibers in the colloidal range. Their growth is just about linear with re spect to time after a period of about 1 hour. The briquette or pellet size used is also a variable which effects the time at given temperatures, especially in a continuous process, such as that carried out in the rotary kiln where the pellet is heated gradually to the desired temperature. Radiant heat causes the temperature on the surface of the lump to rise faster than that within its interior and forms an envelope of small fibers around the pellet or briquette. These fibers, due to their ability to reflect radiation, tend to slow down heat penetration into such interior. It will be found desirable therefore to heat up slowly the entire compact to about 800 prior to elevating its temperature to the reaction temperature necessary for fiber and particle size formation. This can be effected by adjusting the speed at which the lumps are passing through the low temperature end of a direct fired rotary kiln or shaft furnace. This is particularly a factor in furnaces and continuous processes in which the heating is carried out by radiation, convection and conduction.

The fiber-containing reaction mixture obtained when a salt matrix is employed will be somewhat cemented together. It is then necessary to separate the fibers from the salt matrix and unreacted materials. In such instances, the procedures used for separating the fibers into various desired size ranges will differ in some aspects. In general, fiber separation from the reaction mixture is effected by leaching out the unreacted materials and the matrix salt in aqueous slightly acidic solution. On dissolving out the unreacted material and salt, the fibers are filtered and washed free of undesired materials with water prior to drying.

Colloidal size fibers can readily be separated in this manner by first grinding the kiln efiluent into a pulverized mass and then by leaching the resulting material with water, using a high speed agitator, until unreacted materials present are dissolved. The aqueous blend, which is usually at a pH above 11, is then adjusted with a mineral acid or organic acid such as acetic acid to a pH of about 9-1l. The resulting slurry is then passed 4-6 times through a colloid mill or other similar type mill until the fibers separate from coarse, unreacted particles which are emitted with the undispersed kiln efiluent. The slurry-containing coarse material is then passed through a centrifuge or similar type separatory apparatus to remove said coarse particles from the colloidal suspension of fibers. The colloidal suspension, free of large coarse particles, must then be fiocculated in such manner that the colloid can be filtered and dried without agglomeration or recementing of the fiber. This requires special handling techniques different from those applied to larger or insulating sized fibers. To effect such flocculation, the suspension is first acidified to a pH of 6.5 by the incorporation of sufficient organic or inorganic cation-active compound, preferably a commercial type cationic ion-exchange resin which will replace the alkali metal cations in solution with protons and enable removal of the cationic solution through filtering from the colloid dispersion. Other useful forms of commercially available cationic ion-exchange compositions are those of the nuclear-sulfonic type, phenolicmethylene-sulfonic type, sulfonated coal types and carboxylic types. Inorganic types including aluminum silicate, silicic acid, etc. Upon freeing the dispersion of cations, anion removal must be undertaken which can be readily brought about by incorporating in the dispersion a suflicient amount of a conventional type weakly or strongly basic anion-exchange compound, preferably a commercially available 19 anion-exchange resin essentially to replace anions present with hydroxyl groups and in such manner that the displaced anions can be removed through filtering treatment. Upon cation and anion removal, flocculation of the colloidal particles is effected and by adding a conventional type flocculating agent, such as alum, or other suitable flocculating agents in minute traces containing cations such as manganese, zinc, copper, etc. The flocculated material can then be collected in a basket centrifuge or other suitable filtration equipment and dried at about 100 C.

Kiln discharge containing larger pigmentary or insulation size fiber material can be quenched directly as it issues from the kiln or it can be cooled, ground and then added to demineralized Water as illustrated in the examples for the purpose of leaching out the fused salt present. Except in processing colloidal fibers the use of deionized water is not a requirement. One satisfactory method of separation comprises placing the kiln discharge in large tanks purged with 90 C. deionized water. Fresh demineralized water is continuously supplied to the tanks and until the leachings are found to be essentially free of halides and caustic. Fibrous titanate bundles in the shape of briquettes or pellets of the original sizes that were added to the kiln are then placed on trays to be dried. Unlike the colloidal particles, exfoliation of the dry patricles can be effected by passing the material into and grinding it in a colloid type mill. Such grinding can be undertaken in several different ways. In preparing pigmentary and insulating size fibers, some treatment is necessary to remove any undesired larger sized or smaller sized particles, lumps of foreign material or agglomerates which might adversely affect their usefulness particularly in paper applications. The refining stages to which these fibrous materials are subjected can consist of many steps. Usually, these entail a first step of grinding the freshlyleached lumps to a size of about 4 mesh screen; mixing the ground lumps with water to form an approximate 10% slurry; and then passing this slurry into an attrition mill set at about 1-5 mils for further treatment. Thereafter, the resulting material is diluted with water to about 1% solids and is passed through conventional separators to remove undesired large particles of grit. This can be carried out on a continuous recycle basis until all material passes particular standards. Upon requisite particle size being attained, the material is allowed to stand in large decantation tanks prior to filtration and flocculation treatment. Obviously methods are selected to minimize mechanical damage to the fibers.

As exemplified in the examples, the pigmentary fibrous titanates of this invention are particularly useful as inorganic pigmenting ingredients in paper manufacture. In such applications they advantageously reduce costs and impart high, increased opacity and brightness characteristics to the paper without any appreciable decrease in bursting strength. In addition the resulting paper product exhibits improved printability characteristics, especially in offset printing applications. The fibrous pigment is adaptable to any type of papermaking procedure which generally involves mixing the pigment, starch and other desired paper ingredients with the pulp slurry and preferably after the pulp has been suitably beaten in accordance with usual papermaking practice. Since the pigmentary titanate fibers disperse easily in paper pulp and are not seriously affected by the dispersing action of starch, they will be found to provide much greater pigment retention in the sheet than it provided with TiO when starch is present. Thus, when the paper retention properties of the fibrous pigment are compared with a titanium dioxide pigment a to better retention will be found to obtain for the fibrous pigment product of this invention.

The improvements thus afforded by reason of such fibrous titanate pigment employment in papermaking will vary somewhat depending on the pulps used but generally enhancement in opacity and other desired paper characteristics will inherently result with the use of all pulps and combinations. Following dispersion of the pigmenting titanate in the pulp, the pH of the slurry is adjusted to within the range 4.5 to 6.5, and preferably to about pH of 5, by adding a flocculating agent such as aluminum sulfate, a salt of sulfuric acid or sulfuric acid per se. The acidified slurry is then transferred to the head box of a conventional papermaking apparatus, e.g. a Fourdrinier or cylinder machine and is sheeted into paper.

Although titanates with TiO /M O stoichiometry of 5/1 to 8/1 are preferred for use in such. applications, the tetratitanates of potassium and sodium as well as sodium and potassium hexatitanates or mixtures of such titanates are also advantageously useful. Potassium hexatitanate fibers within the average diameter from 0.1 to 0.4 micron with lengths of 5-100 microns afford retention and overall pigment properties and hence are especially useful. For optimum retention, dispersion and opacity, preferred diameter and length sizes for either sodium or potassium fibrous titanates comprise from 0.2 to 0.3 micron in diameter and lengths of from 10 to 50 microns.

Sufficient titanate pigment is added to constitute from about 0.5 to 30% of the pulp on a dry basis. Ash values of the paper, by virtue of the high pigment retention obtained, will range from about 20% to 65% or of the pigment concentration in the slurry on a dry pulp basis.

The invention is not limited to the addition of the fibrous titanate in the heater or doping box. The pigment may also be incorporated in paper coatings and folding boxboard during or after the drying step. In folding boxboard applications, the titanate pigment plus starch coatings crack less on bending than coatings made from TiO and starch.

The titanate fibers in preferred diameter range bend easily to decrease the abrasive wear on the Fourdrinier screen. This decreased abrasion is attributed to the intrinsic softness of the fibers, the entrainment of the paper pulp, and the alignment of the fibers on the moving screen. Such reduced abrasion also reduces the wear on the punches, slitter knives and trimmer blades which decreases slitter dust contamination of printing plates in the letter press and blankets in the off-set press.

A further improvement which the invention affords in papermaking, particularly when 10% and over of the fibrous titanate pigment is present in the paper arises from the high melting point of the fibers. Because titanate fibers do not melt or disintegrate below 1150 C. and the thin interwoven fibers retain a structural network similar to cellulose paper, papers containing them advantageously retain sheet form and legibility of printing or writing after burning and thereby afford a desired preservation of records.

Another feature of titanate pigment use in paper is the retardation against paper ageing which they provide. Yellowing and ageing is considered to be due to acid attack on the cellulose fibers, generated by hydrolysis of alum coagulating agent employed in papermaking. Alkali metal titanates possess residual alkalinity which advantageously neutralizes and prevents the very slow undesired acid attack on cellulose.

Advantageously, this invention affords improved methods for producing novel forms of colloidal, pigmentary or insulating grades of fibrous alkali metal titanates in desired, uniform and requisite fiber dimension. This is achieved by a controlled, uniform heating, in essentially dry state, of the specified ratios of reactants in relatively small, preferably modular state, e.g. less than 2" and preferably leSs than /2" size, to insure uniform heating throughout the entire charge to the peak temperature requisite for heat soak.

We claim:

1. A method for producing fibrous, water-insoluble alkali metal titanates in predetermined diameter-to-length size containing a molar ratio of TiO /M O (M being an alkali metal) of from 4:1 to 9: 1, comprising calcining and reacting under essentially dry, non-fluid conditions a previously dry-blended, nodular compacted mixture of suflicient basic, water-soluble oxygen-containing alkali metal compound selected from the group consisting of an oxide, hydroxide, salt, and mixtures thereof, with an oxygen-containing titanium compound yielding TiO in the reaction, employing in the process calcination temperatures ranging from 200- 850 C. when producing a predominantly colloidal size titanate having particle dimensions ranging from 0.005- 0.1 micron diameter and lengths at least 10 times said diameter; calcination temperatures ranging from 850- 975 C. when producing a predominantly pigmentary size titanate having particle dimensions ranging from 0.1-0.6 micron in diameter and length 10-100 times said diameter; and calcination temperatures ranging from 975- 1150 C. when producing a predominantly insulating size titanate having particle dimensions ranging from 0.6-3.0 microns in diameter and lengths from 100-1000 times said diameter, leaching the titanate reaction product from the calcination to remove undesired reaction products therefrom, and then filtering, exfoliating, drying and recovering the desired fibrous titanate product.

2. The process of claim 1 in which the basic oxygencontaining alkali metal compound is a potassium compound.

3. The process of claim 1 in which the basic oxygencontaining alkali metal compound is a sodium compound.

4. The process of claim 1 in which calcination temperatures ranging from 600-825 C. are used in the production of a predominantly colloidal size titanate.

5. The process of claim 1 in which the oxygen-containing titanium compound is mineral rutile.

6. The process of claim 1 in which the oxygen-containing titanium compound is TiO 7. The process of claim 1 in which the compacted reaction mixture subjected to calcination additionally contains from 10 to 30% by weight of an alkali metal halide.

8. The process of claim 4 in which the basic oxygencontaining alkali metal compound is a potassium compound.

9. The process of claim 4 in which the basic oxygencontaining alkali metal compound is a sodium compound.

10. The process of claim 4 in which the compacted mixture being calcined contains a molar ratio of titanium compound to alkali metal compound, calculated as TiO M 0, ranging from 2:1 to 8:1.

11. The process of claim 1 in which the dry, compacted mixture subjected to calcination additionally contains about from 5-65%, by weight, of an alkali metal halide.

12. The process of claim 11 in which the basic oxygencontaining alkali metal compound is a sodium compound and the alkali metal halide is sodium halide.

13. The process of claim 11 in which the basic oxygencontaining alkali metal compound is a potassium compound and the alkali metal halide is a potassium halide.

14. The process of claim 11 in which the oxygen-containing titanium compound is mineral rutile.

15. A method for preparing a fibrous water-insoluble alkali metal titanate containing a molar ratio of TiO M (M being an alkali metal) of from 4:1 to 9:1 and in predetermined diameter-to-length size and predominantly colloidal with at least 50% of its particles ranging in size from 0005-01 microns diameter with lengths at least ten times said diameter, comprising calcining under essentially dry-non-fiuid reaction conditions a previously dryblended, nodular, compacted mixture of (1) TiO (2) a basic water-soluble oxygen compound of an alkali metal selected from the group consisting of an oxide, hydroxide, salt, and mixtures thereof, in a molar ratio of TiO to alkali metal oxygen compound of from 2:1 to 8: 1, and (3) -45 parts by weight of an alkali metal chloride, eifecting said calcination at temperatures ranging from 600-850 C. until conversion to the alkali metal titanate is obtained,

22" and then leaching, filtering, drying and recovering the resulting fibrous colloidal titanate.

16. A method for preparing a fibrous water-insoluble alkali metal titanate containing a molar ratio of TiO /M O (M being an alkali metal) of from 4:1 to 9:1 and in predetermined diameter-to-length ratio with at least 50% of the titanate particles in insulating size having dimensions ranging from 0.6-3.0 microns in diameter and lengths -1000 times said diameter, comprising calcining under essentially dry, non-fluid conditions and in the form of a compacted, nodular dry-blended reaction mixture, 20-80 parts by weight of TiO 7-65 parts by weight of a basic water-soluble oxygen compound of an alkali metal selected from the group consisting of an oxide, salt and mixtures, and from 5-45 parts by weight of an alkali metal chloride, effecting said calcination at temperatures ranging from 975-1100" C. and until conversion to the desired titanate is obtained and thereafter leaching, filtering, exfoliating, drying and recovering the fibrous insulating form of titanate product.

17. A method for preparing fibrous water-insoluble potassium titanate useful in constructing insulating blocks, said titanate being in predetermined diameter and length size with at least 50% of its particles ranging in dimension from 0.6-3.0 microns in diameter and 100-1000 times the diameter in length, comprising calcining under essentially dry, non-fluid conditions and at a temperature ranging from 975-1050 C. a compacted, nodular dry-blended reaction mixture consisting of 45-55% by weight of KCl, the remainder being TiO and an alkali metal compound selected from the group consisting of KHCO K CO and KOH, employing in the mixture a molar ratio of TiO K 0 of about 3:1, eifecting said calcination until conversion to potassium titanate is obtained, quenching the resulting calcined reaction product in water, and then filtering, exfoliating, drying and recovering the fibrous pigmentary potassium titanate.

18. A method for producing fibrous water-insoluble potassium titanate useful as loose bulk insulating material, said titanate being in predetermined diameter and length size with at least 50% of its particles ranging in dimension from 0.6-3.0 microns in diameter and 100- 1000 times said diameter in length, comprising calcining at a temperature ranging from 975-1075 C. under essentially dry, non-fluid conditions, a nodular compacted previously dry-blended reaction mixture consisting of 20- 30%, by weight, of KCl, the remainder being T102 and an alkali metal compound selected from the group consisting of KHCO K CO and KOH, employing in the reaction mixture a molar ratio of TiO /K O of about 3.5 :1, continuing said calcination until conversion to potassium titanate is obtained, quenching the resulting calcined reaction product in water, and then filtering, exfoliating, drying and recovering the fibrous pigmentary potassium titanate product.

19. A method for producing fibrous water-insoluble potassium titanate useful as a paper pigment, said titanate being in predetermined diameter and length size with at least 50% of its particles ranging in dimension from 0.1- 0.6 micron in diameter and 10-100 times the diameter in length, comprising calcining under essentially dry, nonfiuid conditions and at a temperature ranging from 850- 975 C. a compacted pelletized dry-blended reaction mixture consisting of 20-30% by weight of KCl, the remainder being TiO and an alkali metal compound selected from the group consisting of KHCO K CO and KOH, employing in the mixture a molar ratio of TiO /K O of about 3.5 :1, continuing the calcination until conversion to the desired fibrous potassium titanate is attained, quenching the pelletized calcined reaction product in water, and then filtering, exfoliating, drying and recovering the pigmentary fibrous product.

20. A method for producing fibrous water-insoluble potassium titanate useful in boxboard paper, said titanate being in predetermined diameter and length size with at least 50% of its particles ranging in dimension from 0.1- 0.6 micron in diameter and 10-100 times the diameter in length, which comprises calcining under essentially dry, non-fluid conditions and at a temperature from 850- 975 C., a compacted, previously dry-blended pelletized mixture consisting of 20-30% by Weight of KCl, the remainder being TiO and an alkali metal compound selected from the group consisting of KHCO K CO and KOH, employing in the mixture a molar ratio of TiO to K of about 4: 1, continuing the calcination until conversion to said titanate is attained, quenching the resulting pelletized reaction product in Water, and then filtering, exfoliating, drying and recovering the desired titanate product.

21. A method for producing fibrous Water-insoluble potassium titanate, useful as insulating pigment said titanate being in predetermined diameter and length size with at least 50% of its particles ranging in dimension from 0.1-O.6 micron in diameter and -100 times the diameter in length, which comprises calcining at a temperature ranging from 975-1050" C. under essentially dry, nonfluid conditions, a compacted, nodular, previously dryblended reaction mixture consisting of 5-30% by Weight of KCl, the remainder being TiO and an alkali metal compound selected from the group consisting of KHCO K CO and KOH, employing in said mixture a molar ratio of TiO to K 0 of about 4.5 :1, quenching the resulting reaction product in Water and then filtering, exfoliating, drying and recovering the desired pigmentary titanate fibers.

22. A process for preparing a fibrous water-insoluble potassium titanate in predominantly pigmentary size dimension with at least 50% of its particles ranging from 0.1-0.6 micron in diameter and at least 1'0-100 times the diameter in length which comprises, subjecting a compacted, previously dry-blended, pelletized reaction mixture containing, by Weight, 50% titanium dioxide, 25% potassium chloride and 25% potassium carbonate to calcination under essentially dry-non-fluid conditions in a rotary calciner at temperatures ranging from 875-975 C.

until conversion to potassium titanate is effected, quenching the pelletized calciner reaction product through discharge in water and leaching said product free of chloride salts, separating the fibrous particles by subjecting a dilute slurry thereof to milling treatment and until said pigmentary size titanate fibers remain, fiocculating and then filtering said dilute slurry and then drying and recovering the desired fibrous pigmentary potassium titanate.

23. A method for preparing fibrous water-insoluble alkali metal titanate containing a molar ratio of TiO /M O (M being an alkali metal) of from 4:1 to 9:1 in predetermined diameter-to-length ratio and predominantly pigmentary in size with at least of its particles having dimensions ranging from 0.1-0.6 micron in diameter and lengths 10-100 times said diameter, comprising calcining, under essentially dry, non-fluid conditions and in the form of a nodular compacted, previously dry-blended mixture, (1) TiO (2) a basic Water-soluble oxygen compound of an alkali metal selected from the group consisting of an oxide, hydroxide, salt, and mixtures of said compounds, in a molar ratio of TiO to M 0 (M being an alkali metal) of from 2:1 to 8:1, and (3) 5-45 parts by weight of an alkali metal chloride, eitecting said calcination at temperatures ranging from 850-975 C. until conversion to an alkali metal titanate is obtained, and then quenching, leaching, filtering, exfoliating, drying and recovering the resulting fibrous pigmentary product.

References Cited UNITED STATES PATENTS 2,833,620 5/1958 Gier et al 23-51 2,841,470 7/1958 Berry 23-51 2,924,549 2/1960 Klein et al 162l62 3,129,105 4/1964 Berry et al. 106-299 X OSCAR R. VERTIZ, Primary Examiner.

H. T. CARTER, Assistant Examiner. 

1. A METHOD FOR PRODUCING FIBROUS, WATER-INSOLUBLE ALKALI METAL TITANATES IN PREDETERMINED DIAMETER-TO-LENGTH SIZE CONTAINING A MOLAR RATIO OF TIO2/M2O (M BEING AN ALKALI METAL) OF FROM 4:1 TO 9:1, COMPRISING CALCINING AND REACTING UNDER ESSENTIALLY DRY, ON-FLUID CONDITIONS A PREVIOUSLY DRY-BLENDED, NODULAR COMPACTED MIXTURE OF SUFFICIENT BASIC, WATER-SOLUBLE OXYGEN-CONTAINING ALKALI METAL COMPOUND SELECTED FROM THE GROUP CONSISTING OF AN OXIDE, HYDROXIDE, SALT, AND MIXTURES THEREOF, WITH AN OXYGEN-CONTAINING TITANIUM COMPOUND YIELDING TIO2 IN THE REACTION, EMPLOYING IN THE PROCESS CALCINATION TEMPERATURES RANGING FROM 200850*C. WHEN PRODUCING A PREDOMINANTLY COLLOIDAL SIZE TITANATE HAVING PARTICLE DIMENSIONS RANGING FROM 0.0050.1 MICRON DIAMETER AND LENGTHS AT LEAST 10 TIMES SAID DIAMETER; CALCINATION TEMPERATURES RANGING FROM 850975*C. WHEN PRODUCING A PREDOMINANTLY PIGMENTARY SIZE TITANATE HAVING PARTICLE DIMENSIONS RANGING FROM 0.1-0.6 MICRON IN DIAMETER AND LENGTH 10-100 TIMES SAID DIAMETER; AND CALCINATION TEMPERATURES RANGING FROM 9751150*C. WHEN PRODUCING A PREDOMINANTLY INSULATION SIZE TITANATE HAVING PARTICLE DIMENSIONS RANGING FROM 0.6-3.0 MICRONS IN DIAMETER AND LENGTHS FROM 100-1000 TIMES SAID DIAMETER, LEACHING THE TITANATE REACTION PRODUCT FROM THE CALCINATION TO REMOVE UNDESIRED REACTION PRODUCTS THEREFROM, AND THEN FILTERING, EXFOLIATING, DRYING AND RECOVERING THE DESIRED FIBROUS TITANATE PRODUCT. 